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#11
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Kenwood R-1000
On 4/17/2016 4:33 PM, DhiaDuit wrote:
On Sunday, April 17, 2016 at 1:48:00 PM UTC-5, G Cornelius wrote: On 04/16/2016 04:00 AM, analogdial wrote: Tubes last alot longer than paper and electrolytic capacitors. Now there's a blanket statement if I ever heard one. My experience with the tube era was that a power supply would commonly have problems with either the rectifier tube or the electrolytics. Back then - as a teen, that is - I was a lot better at replacing tubes and swapping out electrolytics than I was at anything else, so take this with a grain of salt, but there did seem to be a lot of tube failures. The tubes that ran hot in the miniature tube versions of the All American Five radio - the 50C5 output tube and the 35W4 (?) rectifier - were the usual suspects. Nowadays tube radios, etc., seem to be showpieces and not actually used, with those ancient capacitors continuing to age while the tube filaments remain intact; so, today at least, the old tubes last way longer than those ancient capacitors! George P.S. The All American Five in my garage is still plugged in and still works fine at almost 50 years of age. Likely had a tube or two replaced over the years and little else. Do you remember that many stores had tube testers and some of those stores sold tubes too? I reckymember them. I'm old enough to remember those well. I had a beast Hallicrafters short wave tube radio that I'd stay up much too late listening to. Good memories. |
#12
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Kenwood R-1000
On Monday, April 18, 2016 at 1:50:57 AM UTC-5, Mike S wrote:
On 4/17/2016 4:33 PM, DhiaDuit wrote: On Sunday, April 17, 2016 at 1:48:00 PM UTC-5, G Cornelius wrote: On 04/16/2016 04:00 AM, analogdial wrote: Tubes last alot longer than paper and electrolytic capacitors. Now there's a blanket statement if I ever heard one. My experience with the tube era was that a power supply would commonly have problems with either the rectifier tube or the electrolytics. Back then - as a teen, that is - I was a lot better at replacing tubes and swapping out electrolytics than I was at anything else, so take this with a grain of salt, but there did seem to be a lot of tube failures. The tubes that ran hot in the miniature tube versions of the All American Five radio - the 50C5 output tube and the 35W4 (?) rectifier - were the usual suspects. Nowadays tube radios, etc., seem to be showpieces and not actually used, with those ancient capacitors continuing to age while the tube filaments remain intact; so, today at least, the old tubes last way longer than those ancient capacitors! George P.S. The All American Five in my garage is still plugged in and still works fine at almost 50 years of age. Likely had a tube or two replaced over the years and little else. Do you remember that many stores had tube testers and some of those stores sold tubes too? I reckymember them. I'm old enough to remember those well. I had a beast Hallicrafters short wave tube radio that I'd stay up much too late listening to. Good memories. Vacuum Tube Testers Youtube |
#13
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Kenwood R-1000
Michael Black wrote:
I gather those with HRO-500s have had some problem replacing germanium transistors (and probably the germanium transistors need replacing because they've gone bad over time). Germanium transistors are cheap and plentiful on eBay. You need to figure out which ones made in the Soviet Union replace the ones made in the west. Germanium transistors were mostly PNP, so NPN ones are harder to find. Replacements for CK722, 2n404, 2n107 and 2n109 are less than a $.25 each including postage. I am sure there are others, but those were the ones I needed. I found 100 assorted Tesla (eastern Europe, not actually Soviet) ones for less than $.50 each including postage. Geoff. -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 |
#14
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Kenwood R-1000
On Wed, 20 Apr 2016, Geoffrey S. Mendelson wrote:
Michael Black wrote: I gather those with HRO-500s have had some problem replacing germanium transistors (and probably the germanium transistors need replacing because they've gone bad over time). Germanium transistors are cheap and plentiful on eBay. You need to figure out which ones made in the Soviet Union replace the ones made in the west. Germanium transistors were mostly PNP, so NPN ones are harder to find. Replacements for CK722, 2n404, 2n107 and 2n109 are less than a $.25 each including postage. I am sure there are others, but those were the ones I needed. At least some of those are audio bandwidth transistors, the HRO-500 of course needs transistors good in the shortwave and low VHF segment. I just know I've seen people writing about restoring their HRO-500s and other things with germanium diodes, and getting replacements has been some sort of an issue. I probably have some germanium transistors around, unless I tossed them. There was a period in the seventies when the local electronic store, which also sold surplus (Etco Electronics, they later moved their base to the US to do mailorder) was offering great deals on germanium transistors, but their selling point wasn't that they were germanium. It was that they had good frequency response. I did buy a lot of those back then. In some ways it is a surprise the HRO-500 could come out in 1964. It's not that long before that transistors were for audio and at best the AM broadcast band, yet here is a receiver that from reports is fairly good, it wasn't a consumer radio, but which could be transistorized. The big wave of transistor shortwave receivers came towards the end of the sixties, and some, like my Hallicrafters S-120A, were awful, in part because they were transistorized. Lots of overload, on top of the usual issues related to low end receivers. Michael |
#15
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Kenwood R-1000
G Cornelius wrote:
On 04/16/2016 04:00 AM, analogdial wrote: Tubes last alot longer than paper and electrolytic capacitors. Now there's a blanket statement if I ever heard one. My experience with the tube era was that a power supply would commonly have problems with either the rectifier tube or the electrolytics. Series string sets are harder on tubes than transformer sets. Open heaters and HK shorts are the usual failures. A thermistor used as an inrush current limiter helps. The failure rate for paper caps must be close to 100% by now. That doesn't mean that the circuit no longer works but that the leakage is now out of spec and they will only get worse in the future. I doubt there's been a decent paper wrapped elecrolytic seen for at least 20 years. I seem to recall reading that some small signal tubes are rated for a life of 20,000 hours. Or was it 50,000 hours? Anyway, 20,000 hours at 4 hours a day is about 14 years. Maybe twice that long before the radio actually goes deaf. I like to fix up old radios and I very rarely find tubes with low gain. As I mentioned, the occasional common failure modes are open heaters and HK shorts. I have a strong suspicion that most of the tubes replaced in the past were still useable. A gently aging tube might work quite well at normal voltages but be an underperformer in a circuit in which a leaky screen bypass cap is pulling down the voltage. A new tube might perk up the circuit but the real problem is the leaky cap. And it was common repair shop practice to knowingly replace good parts such as tubes. Shocking, I know! And I understand why. I was a new tech at a shop, and a customer called in about her microphone preamp all of the sudden having distorted sound. I asked the obvious question "Did you put new batteries in?" "Yesssss! Of course I put new batteries in!!!!!!!! Do "you think I am an idiot??!!!" Needless to say, her "new" batteries were just as dead as the first set. Stupid me, I thought she'd be pleased that new batteries that actually worked brought the preamp back to perfect operation. "YOU CHARGED ME THAT MUCH (our minimum charge, actually pretty cheap) JUST TO REPLACE THE BATTERIES!! YOU'RE A DAMN CROOK!!!!" No, if I was a crook, I could have charged her five times as much for replacing good parts and we both would have been so much happier that day. Long story short, tubes get an largely undeserved bad rap for unreliability. |
#16
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Kenwood R-1000
On Fri, 22 Apr 2016, analogdial wrote:
G Cornelius wrote: On 04/16/2016 04:00 AM, analogdial wrote: Tubes last alot longer than paper and electrolytic capacitors. Now there's a blanket statement if I ever heard one. My experience with the tube era was that a power supply would commonly have problems with either the rectifier tube or the electrolytics. Series string sets are harder on tubes than transformer sets. Open heaters and HK shorts are the usual failures. A thermistor used as an inrush current limiter helps. The failure rate for paper caps must be close to 100% by now. That doesn't mean that the circuit no longer works but that the leakage is now out of spec and they will only get worse in the future. I doubt there's been a decent paper wrapped elecrolytic seen for at least 20 years. And the stuff wasn't intended for perpetual use. It was "average stuff" intended to be used, and then eventually fade away. Indeed, it was tossed. SSB came along, making a lot of stuff "obsolete", transistors came along and people wanted that. So in the late sixtes and early seventies, the old AM and tube equipment was relatively cheap. There was a period when I was getting stuff, playing with it a bit, then trading it for something else. Not many were thinking of "collecting", and nostalgia hadn't set in. So that generally caused the stuff to be relegated to the garbage, or the top shelf. It's only in more recent times that the stuff was seen as valuable. So those capacitors that weren't so great to begin with are now decades older. The tubes sitting around didn't age (though I finally stripped some old RCA Carfones, mobile equipment for the trunk of the car, and when I pulled the tubes, a fair number had been broken, even though I don't remember them being in a situation for that, they just sat there for decades), while the capacitors probably kept on aging even when not in use. As I said, it's the way they made capacitors up to a certain point, equipment made after that point didn't use paper capacitors but did use ceramic, so their life is likely in good shape now. Michael |
#17
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Kenwood R-1000
Michael Black wrote:
And the stuff wasn't intended for perpetual use. It was "average stuff" intended to be used, and then eventually fade away. Indeed, it was tossed. SSB came along, making a lot of stuff "obsolete", transistors came along and people wanted that. So in the late sixtes and early seventies, the old AM and tube equipment was relatively cheap. There was a period when I was getting stuff, playing with it a bit, then trading it for something else. Not many were thinking of "collecting", and nostalgia hadn't set in. So that generally caused the stuff to be relegated to the garbage, or the top shelf. It's only in more recent times that the stuff was seen as valuable. So those capacitors that weren't so great to begin with are now decades older. The tubes sitting around didn't age (though I finally stripped some old RCA Carfones, mobile equipment for the trunk of the car, and when I pulled the tubes, a fair number had been broken, even though I don't remember them being in a situation for that, they just sat there for decades), while the capacitors probably kept on aging even when not in use. As I said, it's the way they made capacitors up to a certain point, equipment made after that point didn't use paper capacitors but did use ceramic, so their life is likely in good shape now. Michael The caps probably did age even when not in use. I had some old NOS wax dipped paper caps and they all were leaky. Somewhere in Terman's Radio Engineer's handbook, he says paper caps can be expected to work as new for only a few years or so. He had an example for leakage sensitive circuits in which the usual coupling cap is replaced by two much larger caps in series with a grounded bleeder in between which, presumably, would forestall the capacitor aging problem. Back in the 50s, the higher quality, less disposable electronics, used those newfangled Sprague Black Beauty capacitors in place of the run of the mill wax dipped paper caps. I suppose that toxic, short circuit mess hadn't fully devloped by the mid 60s, when Sprague retained the name "Black Beauty" for their axial lead mylar film caps. The "Orange Drop" name for radial lead caps is still around, of course. Mylar caps replaced paper caps at about time electronics started going solid state so it's understandable why people associate the unrelibility problems with tubes. |
#18
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Kenwood R-1000
Michael Black wrote:
At least some of those are audio bandwidth transistors, the HRO-500 of course needs transistors good in the shortwave and low VHF segment. I expect they are there too. The ones I am interested are for yellow boxes made around 1963 which use audio transistors. Most of them are either oscillators to boost DC voltage, some are dc amplifiers. I just know I've seen people writing about restoring their HRO-500s and other things with germanium diodes, and getting replacements has been some sort of an issue. The Soviet D9b diodes make great detectors and are about a penny each, including postage. They were half that because the lower case b in the Cyrilic (Russian) alphabet looks like a number 5, and they were listed as D95 diodes, which no one could find any specs on. I think I had something to do with the price rise, when I commented on the price on several groups, the listings were fixed and the price went up. There even are 1n34a diodes still made with germanium in them. Most of the so called germanium diodes are actualy silicon. They make finding the real ones difficult as eBay vendors don't differentiate. I have a few UK germanium diodes, that have real gold in them, and are much better detectors. I found them on eBay for 1 UKP each. I am saving them for a special project, when I think of it. I probably have some germanium transistors around, unless I tossed them. There was a period in the seventies when the local electronic store, which also sold surplus (Etco Electronics, they later moved their base to the US to do mailorder) was offering great deals on germanium transistors, but their selling point wasn't that they were germanium. It was that they had good frequency response. I did buy a lot of those back then. If you can look up what they were, I would be interested in finding out. Geoff. -- Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379 |
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